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His last weekend I finally put my boiler, (gas fired, Burnhard), on line and had a rude surprise when the house would not get over 66 deg F. I bled all the baseboards and changed out the batteries in the thermostat. no change. The boiler cycles on and stays on , I have some 40' of head pressure, and the makeup v/v is wide open. the low water control is not giving any warnings. there are 3 legs coming out of the boiler outlet one for the basement, one for the 1st floor and one for the 2nd floor. I notice that the circ p/p is hot as is the piping immediately downstream of the p/p. however, as I move farther away from the p/p the piping begins to cool. I can feel no vibration at the p/p nor hear any sound from the p/p when I use a screwdriver as a "stethascope".I believe the circ p/p has gone south, but barring the use of a guage on the discharge side do not know how to be sure. My backround was, (20 years ago), in marine steam engine rooms, (antique 450 lb sectional headers and 900 lb M types with controlled superheat), and so, don't feel to be on 100% solid ground with this. Can the expansion tank possibly be the culprit?I hope someone out there can offer a little insight . Thanks